Most heavy-duty vehicles include a powertrain driven by an internal combustion (IC) engine. During operation, these engines produce high temperature exhaust gases, as well as particulate matter, such as soot. For such vehicles, particularly those having diesel engines, the products of engine combustion are typically discharged through vertical exhaust stacks to an area above the vehicle cab. Discharging the gases in this manner reduces the amount of exhaust gases and particulate matter that are blown onto the portion of the vehicle located to the rear of the exhaust stack. This, in turn, reduces the potential for heat damage to the vehicle, as well as the unsightly accumulation of soot on the vehicle. Discharging the exhaust gases at an elevated location also decreases the risk that a person standing near a vehicle with a running engine will be directly exposed high temperature exhaust.
Vertical exhaust stacks are typically positioned along the side of the vehicle cab, to the rear of the vehicle door. In order to simplify the design and to avoid the problems inherent with ducting hot exhaust gases through an interior portion of the vehicle, the vertical exhaust stacks generally extend vertically along an outside portion of the cab, from the bottom of the cab to a discharge point positioned above the cab. Although routing the exhaust stack along an exterior portion of the vehicle cab simplifies the exhaust system configuration, exposing the exhaust stack and, therefore, the exhaust pipe to the air stream creates drag, thereby reducing the aerodynamic efficiency of the vehicle. Thus, it is desirable to provide an exhaust stack that creates less drag than currently known exhaust stacks.